A theory of self-organization of an excitable membrane formed on the protoplasmic droplet isolated from Nitella

The process of self-organization of an excitable membrane of protoplasmic droplet of Nitella is studied theoretically by taking the interaction of the local electric current caused by the spatially non-uniform distribution of active domains into account. The theoretical model employed is that the surface membrane forms a mosaic structure composed of lipids and protein molecules, and that each element of the mosaic structure (domain) on the membrane has two distinct conformations corresponding to excited and resting states. The molecules constituting the membrane are derived from the inside of the protoplasm by diffusion. The excitability of the surface membrane appears suddenly after a morphogenetic structure of the membrane is formed with time on the surface of droplet. Time courses of the variation in membrane potential and in membrane resistance are calculated, and the results are compared with experimental data obtained with the protoplasmic droplet of Nitella.